When an exception is thrown from `AnimationTimer::handle`, the JavaFX
application freezes. The reason is that the user exception will bubble up into
framework code, preventing the normal operation of JavaFX.
The following program demonstrates the defect:
public class FailingAnimationTimer extends Application {
@Override
public void start(Stage stage) throws Exception {
var button = new Button("start timer");
button.setOnAction(_ -> {
var timer = new AnimationTimer() {
@Override
public void handle(long l) {
throw new RuntimeException("foo");
}
};
timer.start();
});
var root = new HBox();
root.getChildren().add(new TextField("test"));
root.getChildren().add(button);
stage.setScene(new Scene(root));
stage.show();
}
}
The solution is to not allow user exceptions to bubble up into animation
framework code. If an exception occurs, it is instead sent to the current
thread's uncaught exception handler. This is the same thing that we already do
for exceptions thrown by invalidation listeners and change listeners.
In addition to that, a failing animation timer has the potential to spam logs,
which is why I introduced a cut-off value at 100 exceptions for each individual
timer, after which no further exceptions from this particular timer are sent to
the uncaught exception handler. After reaching the cut-off value, the following
warning is logged:
`WARNING: Too many exceptions thrown by AnimationTimer, ignoring further
exceptions. The cut-off number can be set with the system property
com.sun.scenario.animation.failingTimerThreshold (current = 100).`
-------------
Commit messages:
- fix
- failing test
Changes: https://git.openjdk.org/jfx/pull/1811/files
Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1811&range=00
Issue: https://bugs.openjdk.org/browse/JDK-8357157
Stats: 224 lines in 2 files changed: 200 ins; 4 del; 20 mod
Patch: https://git.openjdk.org/jfx/pull/1811.diff
Fetch: git fetch https://git.openjdk.org/jfx.git pull/1811/head:pull/1811
PR: https://git.openjdk.org/jfx/pull/1811
